1. Field of the Invention
The present invention relates to a blade for regulating a release oil used in fixing devices, such as those used in electrophotographic copying machines and printers, and also relates to a fixing device for performing heat-pressure fixing of an unfixed image by passing a recording member carrying the unfixed image between fixing members which are in contact with each other under pressure, and to an image-forming apparatus.
2. Description of the Related Art
In a fixing apparatus, such as those used in an electrophotographic copying machine or printer, in general, a fixing roller and a pressure roller, which are heated by halogen heaters or the like, are brought into contact with each other under pressure, and a recording sheet carrying a toner image is transported through the nip to fix the toner image on the recording sheet. Instead of the fixing roller, a fixing belt or a fixing film may be used. Such members for fixing toner are referred to as fixing members.
In order to prevent toner from being offset and to improve releasability (the ability to release toner and foreign matter), a release oil is occasionally used. In many cases, a blade for regulating the release oil is used so that an appropriately small amount of the release oil is uniformly applied. The blade abuts on a roller so that its edge is brought into contact with the roller, and by passing the release oil through the nip thereof, an appropriate amount of the release oil can be uniformly applied.
The blade may be placed so as to abut on an application roller which is in contact with a fixing roller or to directly abut on the fixing roller. It is also known that a similar blade may be placed so as to abut on a pressure roller in order to scrape off excess release oil, excess toner, and dust.
As the blade, a metal blade or a fluororubber blade is usually used. It is also known that the surface of the blade may be coated with a layer composed of a fluorine-containing resin.
Japanese Patent Laid-Open No. 5-158371 discloses a blade for decreasing the mechanical load of a fixing roller, in which a low-friction member composed of a fluorine-containing resin is attached to the outer periphery of a rubber blade which is in contact with the fixing roller. Japanese Patent Laid-Open No. 10-207279 describes an example in which the surface of a rubber member of a blade is coated with a layer composed of a fluorine-containing resin and teaches that the thickness of the layer is preferably set at 25 to 100 xcexcm. Japanese Patent Laid-Open No. 8-146809 discloses a fixing device in which a blade coated with a fluorine-containing resin is used as a blade abutting on a pressure roller, and as the fluorine-containing resin, a layer composed of a fluorine-containing resin is used.
A blade which supplies a release oil to a fixing member must uniformly regulate the oil and must maintain its function for a long period of time. In particular, recently, since the amount of coating of the release oil has been reduced, even slight nonuniformity of the release oil may deteriorate the image quality. That is, it is essential to prevent nonuniformity in applying the release oil.
At the same time, the blade for regulating the release oil must have high releasability of foreign matter, such as toner and dust. In particular, when a small amount of the release oil is applied, even slight adhesion of foreign matter may cause nonuniformity in applying the release oil.
Accordingly, it is an object of the present invention to provide a blade which can maintain uniformity in applying release oil for a long period of time.
It is another object of the present invention to provide a fixing device in which release oil can be uniformly applied for a long period of time even when a small amount of the release oil is applied, and to provide an image-forming apparatus using the fixing device.
In accordance with one aspect of the present invention, a blade is placed so as to abut on a fixing member or on a to member which controls the amount of a release oil to be supplied to the fixing member in order to regulate the amount of the release oil to be supplied, and the abutting surface of the blade is composed of a silicone rubber layer.
In accordance with another aspect of the present invention, a blade is placed so as to abut on a fixing member or on a member which controls the amount of a release oil to be supplied to the fixing member in order to regulate the amount of the release oil to be supplied, and the blade includes at least a plate-shaped elastic body and a silicone rubber layer formed on the tip of the elastic body.
In the present invention, since the abutting surface of the blade is composed of the silicone rubber layer, the releasability of foreign matter, such as toner and dust, is improved, and nonuniformity in applying the release oil does not occur.
Additionally, since the blade of the present invention includes the abutting surface composed of the silicone rubber layer, the characteristics of the underlying layer are not greatly impaired, and by appropriately selecting a material for the underlying layer, the following advantages can be obtained. That is, if the underlying layer is composed of an elastic body, a blade having satisfactory elasticity can be obtained. If the underlying layer is composed of a fluororubber, a blade having satisfactory heat resistance can be obtained. If the underlying layer is composed of a silicone rubber, a blade having good compression set characteristics can be obtained. If the underlying layer is composed of an elastic body in which a silicone rubber layer is coated with a fluororubber, a blade having good compression set characteristics and resistance to swelling can be obtained. If the underlying layer is composed of a metal, a blade which can be produced by a simple process is obtainable.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.